CN115954866A - Low-voltage ride-through control method and device for two-stage grid-connected photovoltaic inverter - Google Patents
Low-voltage ride-through control method and device for two-stage grid-connected photovoltaic inverter Download PDFInfo
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Abstract
The application relates to a low voltage ride through control method, device and equipment of a two-stage type grid-forming photovoltaic inverter, wherein valve side reference data obtained by respectively adopting a first control mode and a second control mode with positive and negative sequence voltage and positive and negative sequence current control capacities are adopted through control signals to control positive and negative sequence voltages, so that voltage source characteristics are presented to the outside; positive and negative sequence currents are controlled to flexibly control fault current; the low voltage ride through of the two-stage grid-forming type photovoltaic inverter is realized through the matching of a preceding stage booster circuit and a subsequent stage inverter circuit control strategy, the balance of photovoltaic output power during a fault period and the smooth transition from recovery to grid-forming control after the fault are realized, and the technical problem that the operation of an electric power system is damaged by large current generated after the fault occurs due to the fact that the photovoltaic inverter is applied to the grid-forming control technology in the conventional electric power system is solved.
Description
Technical Field
The application relates to the technical field of new energy control, in particular to a low-voltage ride through control method, device and equipment for a two-stage type grid-structured photovoltaic inverter.
Background
In recent years, new energy power generation has been highly emphasized in energy development strategies and is rapidly developed. High proportion new forms of energy passes through power electronic equipment access electric power system, and electric power system does not possess synchronous generator's characteristic under traditional operating mode, makes electric power system appear inertia reduction, the problem that frequency stability reduces. The concept of network-building type control is provided for solving the problems, and the supporting capacity of the new energy to the frequency and the voltage of the power system is improved by simulating the operating characteristics of the synchronous generator to a certain extent.
The grid-type control technology applied to the photovoltaic inverter of the new energy can improve the supporting capability of the power system, but a large fault current can be generated during the fault period of an external alternating current system, and the safety of a converter is damaged. Therefore, the fault current suppression and fault ride-through strategy of the grid-structured photovoltaic inverter needs to be researched to ensure the safe and stable operation of the inverter.
Disclosure of Invention
The embodiment of the application provides a low voltage ride through control method, device and equipment of a two-stage grid-connected photovoltaic inverter, and is used for solving the technical problem that the existing power system adopts the photovoltaic inverter to be applied to the grid-connected control technology, and large current can be generated after a fault occurs to harm the operation of the power system.
In order to achieve the above object, the embodiments of the present application provide the following technical solutions:
a low voltage ride through control method of a two-stage type grid-structured photovoltaic inverter comprises a preceding stage booster circuit and a subsequent stage inverter circuit, and comprises the following steps:
acquiring electrical quantity parameters of the two-stage grid-structured photovoltaic inverter, wherein the electrical quantity parameters comprise an actual reactive power value, an alternating voltage rated value, an alternating voltage amplitude value, a maximum tolerant current value and a rated current value;
determining a control signal for low-voltage ride through in the two-stage grid-connected photovoltaic inverter according to the alternating-current voltage amplitude;
if the control signal is 0, obtaining first valve side reference data by adopting a first control mode according to the actual reactive power value and the rated value of the alternating voltage, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; controlling the operation of the preceding stage booster circuit by adopting a maximum power point tracking mode;
if the control signal is 1, obtaining second valve side reference data by adopting a second control mode according to the alternating voltage amplitude, the tolerant maximum current value and the rated current value, and controlling the operation of the rear-stage inverter circuit according to the second valve side reference data; and controlling the operation of the preceding stage booster circuit in a direct-current voltage mode.
Preferably, the obtaining of the first valve-side reference data according to the actual value of reactive power and the rated value of ac voltage by the first control method includes:
calculating by adopting a network-building algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value;
carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage loop and a negative sequence voltage loop to obtain a first positive sequence current reference value and a first negative sequence current reference value;
corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing are carried out on the first positive sequence current reference value and the first negative sequence current reference value to obtain corresponding first positive sequence valve side reference voltage and first negative sequence valve side reference voltage;
wherein the first valve side reference data comprises a first positive sequence valve side reference voltage and a first negative sequence valve side reference voltage.
Preferably, obtaining second valve side reference data by a second control manner according to the alternating voltage amplitude, the endured maximum current value and the rated current value comprises:
acquiring a d-axis positive sequence current reference value before the fault of the two-stage type grid-forming photovoltaic inverter according to the control signal of 1;
calculating by adopting a network-building algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value; carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring; calculating and determining a second positive sequence current reference value and a second negative sequence current reference value according to the d-axis positive sequence current reference value, the alternating voltage amplitude, the tolerance maximum current value and the rated current value;
corresponding positive sequence current loops, coordinate transformation and negative sequence current loops and coordinate transformation processing are adopted for the second positive sequence current reference value and the second negative sequence current reference value, and corresponding second positive sequence valve side reference voltage and second negative sequence valve side reference voltage are obtained;
wherein the second valve side reference data comprises a second positive sequence valve side reference voltage and a second negative sequence valve side reference voltage.
Preferably, the determining the control signal for the low voltage ride through in the two-stage grid-connected photovoltaic inverter according to the ac voltage amplitude comprises: if the alternating voltage amplitude is smaller than the voltage threshold value, the control signal is 1, and the two-stage grid-connected photovoltaic inverter is indicated to be in fault in the power system; if the amplitude of the alternating voltage is not smaller than the voltage threshold value, the control signal is 0, and it is indicated that no fault occurs in the power system where the two-stage grid-connected photovoltaic inverter is located.
Preferably, the low voltage ride through control method of the two-stage grid-structured photovoltaic inverter includes: if the fault is cleared, controlling the amplitude of the alternating voltage to be not smaller than a voltage threshold value, and restoring a second positive sequence current reference value and a second negative sequence current reference value in the second control mode to the position before the fault according to a slope ratio; and simultaneously, switching the direct-current voltage mode for controlling the operation of the preceding-stage booster circuit into a maximum power point tracking mode.
The application also provides a low-voltage ride-through control device of the two-stage grid-forming type photovoltaic inverter, the two-stage grid-forming type photovoltaic inverter comprises a preceding-stage booster circuit and a subsequent-stage inverter circuit, and the low-voltage ride-through control device comprises a parameter acquisition module, a control judgment module, a first execution module and a second execution module;
the parameter acquisition module is used for acquiring electrical quantity parameters of the two-stage grid-structured photovoltaic inverter, wherein the electrical quantity parameters comprise an actual reactive power value, an alternating voltage rated value, an alternating voltage amplitude value, a maximum tolerant current value and a rated current value;
the control judgment module is used for determining a control signal for low-voltage ride through in the two-stage grid-connected photovoltaic inverter according to the alternating-current voltage amplitude;
the first execution module is used for obtaining first valve side reference data by adopting a first control mode according to the actual reactive power value and the rated value of the alternating current voltage according to the control signal of 0, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; controlling the operation of the preceding stage booster circuit by adopting a maximum power point tracking mode;
the second execution module is configured to obtain second valve-side reference data in a second control manner according to the ac voltage amplitude, the maximum tolerant current value, and the rated current value, and control operation of the subsequent inverter circuit according to the second valve-side reference data, where the control signal is 1; and controlling the operation of the preceding stage booster circuit in a direct-current voltage mode.
Preferably, the first execution module comprises a first computation submodule, a first processing submodule and a second processing submodule;
the first calculation submodule is used for calculating by adopting a network-building type algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value;
the first processing submodule is used for carrying out amplitude limiting processing on the voltage reference value through the positive sequence voltage loop and the negative sequence voltage loop to obtain a first positive sequence current reference value and a first negative sequence current reference value;
the second processing submodule is used for performing corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing on the first positive sequence current reference value and the first negative sequence current reference value to obtain corresponding first positive sequence valve side reference voltage and first negative sequence valve side reference voltage;
wherein the first valve side reference data comprises a first positive sequence valve side reference voltage and a first negative sequence valve side reference voltage.
Preferably, the second execution module includes a data acquisition sub-module, a second computation sub-module and a third processing sub-module;
the data acquisition submodule is used for acquiring a d-axis positive sequence current reference value of the two-stage type grid-structured photovoltaic inverter before the fault according to the control signal of 1;
the second calculation submodule is used for calculating by adopting a network-building type algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value; carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring; calculating and determining a second positive sequence current reference value and a second negative sequence current reference value according to the d-axis positive sequence current reference value, the alternating voltage amplitude, the tolerance maximum current value and the rated current value;
the third processing submodule is used for performing corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing on the second positive sequence current reference value and the second negative sequence current reference value to obtain corresponding second positive sequence valve side reference voltage and second negative sequence valve side reference voltage;
wherein the second valve side reference data comprises a second positive sequence valve side reference voltage and a second negative sequence valve side reference voltage.
Preferably, the low voltage ride through control device of the two-stage grid-connected photovoltaic inverter comprises a fault clearing module, wherein the fault clearing module is used for controlling the amplitude of the alternating voltage to be not less than a voltage threshold value according to fault clearing, and restoring a second positive sequence current reference value and a second negative sequence current reference value in the second control mode to the positions before the fault according to a slope proportion; and simultaneously, switching a direct-current voltage mode for controlling the operation of the preceding-stage booster circuit into a maximum power point tracking mode.
The application also provides a terminal device, which comprises a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is used for executing the two-stage grid-type photovoltaic inverter low voltage ride through control method according to instructions in the program codes.
According to the technical scheme, the embodiment of the application has the following advantages: the method comprises the steps of obtaining an electrical quantity parameter of the two-stage grid-connected photovoltaic inverter; determining a control signal for low-voltage ride through in the two-stage type grid-structured photovoltaic inverter according to the amplitude of the alternating voltage; if the control signal is 0, obtaining first valve side reference data by adopting a first control mode according to the actual reactive power value and the rated value of the alternating voltage, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; controlling the operation of the preceding-stage booster circuit by adopting a maximum power point tracking mode; if the control signal is 1, obtaining second valve side reference data by adopting a second control mode according to the alternating voltage amplitude, the tolerance maximum current value and the rated current value, and controlling the operation of the rear-stage inverter circuit according to the second valve side reference data; and controlling the operation of the preceding stage booster circuit in a direct-current voltage mode. According to the low voltage ride through control method of the two-stage grid-connected photovoltaic inverter, valve side reference data obtained by a first control mode and a second control mode with positive and negative sequence voltage and positive and negative sequence current control capacities are respectively adopted through control signals, and positive and negative sequence voltages are controlled to externally present voltage source characteristics; positive and negative sequence currents are controlled to flexibly control fault current; the low voltage ride through of the two-stage grid-forming type photovoltaic inverter is realized through the matching of a preceding stage booster circuit and a subsequent stage inverter circuit control strategy, the balance of photovoltaic output power during a fault period and the smooth transition from recovery to grid-forming control after the fault are realized, and the technical problem that the operation of an electric power system is damaged by large current generated after the fault occurs due to the fact that the photovoltaic inverter is applied to the grid-forming control technology in the conventional electric power system is solved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive exercise.
Fig. 1 is a flowchart illustrating steps of a method for controlling a low voltage ride through of a two-stage grid-connected pv inverter according to an embodiment of the present disclosure;
fig. 2 is a control frame diagram of a low voltage ride through control method of a two-stage grid-connected pv inverter according to an embodiment of the present disclosure;
fig. 3 is a control frame diagram of a grid-forming algorithm in the low voltage ride through control method of the two-stage grid-forming type photovoltaic inverter according to the embodiment of the present application;
fig. 4 is a voltage ring frame diagram of a grid-forming algorithm in the low-voltage ride-through control method of the two-stage grid-forming photovoltaic inverter according to the embodiment of the present application;
fig. 5 is a current loop frame diagram of a grid-forming algorithm in the low voltage ride through control method of the two-stage grid-forming pv inverter according to the embodiment of the present disclosure;
fig. 6 is a block diagram of a low voltage ride through control device of a two-stage grid-connected photovoltaic inverter according to an embodiment of the present application.
Detailed Description
In order to make the objects, features and advantages of the present invention more apparent and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is apparent that the embodiments described below are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The embodiment of the application provides a low voltage ride through control method, device and equipment of a two-stage grid-connected photovoltaic inverter, wherein when the two-stage grid-connected photovoltaic inverter is in normal operation, a voltage reference value is obtained through a grid-connected algorithm, and then first valve side reference data is obtained through positive and negative sequence voltage rings and positive and negative sequence current rings to control the two-stage grid-connected photovoltaic inverter; when the two-stage grid-connected photovoltaic inverter is in an AC side symmetric and asymmetric fault, amplitude limiting is output through a positive sequence voltage ring and a negative sequence voltage ring at the initial stage of the fault to inhibit instantaneous current spikes, flexible control of fault current is realized by setting positive sequence current reference values and negative sequence current reference values during the fault, the two-stage grid-connected photovoltaic inverter is balanced to be in output power through the cooperation of a DC voltage control mode, and smooth transition is performed from positive sequence current control to negative sequence current control to grid-connected control after the fault, so that the technical problem that the existing power system is applied to the grid-connected control technology by the photovoltaic inverter, and the operation of the power system is damaged by large current after the fault occurs is solved.
The first embodiment is as follows:
fig. 1 is a flowchart illustrating steps of a method for controlling a low voltage ride through of a two-stage grid-connected photovoltaic inverter according to an embodiment of the present disclosure.
As shown in fig. 1, an embodiment of the present application provides a low voltage ride through control method for a two-stage grid-connected photovoltaic inverter, where the two-stage grid-connected photovoltaic inverter includes a preceding-stage boost circuit and a succeeding-stage inverter circuit, and the low voltage ride through control method includes the following steps:
s1, obtaining electric quantity parameters of the two-stage type grid-forming photovoltaic inverter, wherein the electric quantity parameters comprise an actual reactive power value, an alternating voltage rated value, an alternating voltage amplitude value, a maximum tolerant current value and a rated current value.
It should be noted that, in step S1, the electrical quantity parameters of the two-stage grid-connected photovoltaic inverter are acquired to provide data for the subsequent steps. In this embodiment, the front stage boost circuit is mainly used to control the outlet voltage of the two-stage grid-connected photovoltaic inverter, and the rear stage inverter circuit is mainly used to invert a direct current into a three-phase alternating current. The front-stage boost circuit can be recorded as a front-stage DC/DC circuit, and the rear-stage inverter circuit can also be recorded as a rear-stage VSC circuit.
S2, determining a control signal for low voltage ride through in the two-stage type grid-structured photovoltaic inverter according to the alternating voltage amplitude.
It should be noted that, in step S2, whether the two-stage grid-connected photovoltaic inverter fails or not can be determined according to the ac voltage amplitude obtained in step S1, and then a control signal for controlling the two-stage grid-connected photovoltaic inverter to pass through the low voltage is determined according to whether the two-stage grid-connected photovoltaic inverter fails or not.
Further, the determining a control signal for low voltage ride through in the two-stage grid-connected photovoltaic inverter according to the ac voltage amplitude includes: if the amplitude of the alternating voltage is smaller than the voltage threshold value, the control signal is 1, and the two-stage grid-connected photovoltaic inverter is indicated to be in fault in the power system; if the amplitude of the alternating voltage is not smaller than the voltage threshold value, the control signal is 0, and it is indicated that no fault occurs in the power system where the two-stage grid-connected photovoltaic inverter is located.
Fig. 2 is a control frame diagram of a low voltage ride through control method of a two-stage grid-connected photovoltaic inverter according to an embodiment of the present application, and fig. 3 is a control frame diagram of a grid-connection algorithm in the low voltage ride through control method of the two-stage grid-connected photovoltaic inverter according to the embodiment of the present application.
S3, if the control signal is 0, obtaining first valve side reference data by adopting a first control mode according to the actual value of the reactive power and the rated value of the alternating voltage, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; and controlling the operation of the preceding stage booster circuit by adopting a maximum power point tracking mode.
It should be noted that, in step S3, the first valve side reference data can be obtained by adopting a first control mode according to the actual reactive power value and the rated ac voltage value obtained in step S1 and according to the control signal being 0, and the low voltage ride through control over the two-stage grid-forming type photovoltaic inverter is realized by controlling the operation of the rear-stage inverter circuit by the first valve side reference data and controlling the operation of the front-stage boost circuit by adopting the maximum power point tracking mode. In this embodiment, in the process of controlling the operation of the subsequent inverter circuit according to the first valve side reference data, a trigger pulse signal is obtained through a modulation link according to the first valve side reference data, and then the operation of the subsequent inverter circuit is controlled according to the trigger pulse signal. The modulation link can adopt PWM modulation, the modulation link is a relatively well-known technical means in the field, and the maximum power point tracking mode is also a relatively well-known technical means in the field, so that the details of the modulation link and the maximum power point tracking mode are not described in detail here.
As shown in fig. 2, further, the obtaining the first valve-side reference data by the first control method according to the actual value of the reactive power and the rated value of the ac voltage includes:
calculating by adopting a network construction type algorithm according to the actual value of the reactive power and the rated value of the alternating voltage to obtain a voltage reference value;
carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring to obtain a first positive sequence current reference value and a first negative sequence current reference value;
corresponding positive sequence current loops, coordinate transformation and negative sequence current loops and coordinate transformation processing are adopted for the first positive sequence current reference value and the first negative sequence current reference value, and corresponding first positive sequence valve side reference voltage and first negative sequence valve side reference voltage are obtained;
wherein the first valve side reference data comprises a first positive sequence valve side reference voltage and a first negative sequence valve side reference voltage.
In the embodiment of the present application, as shown in fig. 3, the obtaining of the voltage reference value by using a network-forming algorithm includes: firstly, the actual value Q of the reactive power and the reference value Q of the reactive power are calculated ref Calculating a difference value between the two values to obtain a reactive power difference value; the reactive power difference value and a first control parameter M of a network construction type algorithm are compared q Multiplying to obtain the adjusted reactive power; will adjust the reactive powerRated value V of AC voltage acN Performing superposition processing to obtain a voltage reference value V acref 。
It should be noted that, as shown in fig. 3, the network formation algorithm further includes: acquiring actual direct-current voltage u of two-stage grid-structured photovoltaic inverter dc Reference value u of DC voltage dcref And rated angular frequency omega of alternating current 0 The actual value u of the DC voltage is calculated dc And a DC voltage reference value u dcref The difference between the two values and the second control parameter M of the network-forming algorithm dc Multiplying to obtain an adjustment voltage; superimposing the regulated voltage on the nominal AC angular frequency omega 0 And obtaining the phase angle theta through an integration link of 1/s. Theta is used as a reference angle for positive sequence abc/dq coordinate transformation and positive sequence dq/abc coordinate inverse transformation, and theta is used as a reference angle for negative sequence abc/dq coordinate transformation and negative sequence dq/abc coordinate inverse transformation.
Fig. 4 is a voltage loop frame diagram of a grid-forming algorithm in the low-voltage ride-through control method for the two-stage grid-forming photovoltaic inverter according to the embodiment of the present application, and fig. 4 is a current loop frame diagram of the grid-forming algorithm in the low-voltage ride-through control method for the two-stage grid-forming photovoltaic inverter according to the embodiment of the present application. In FIG. 4, L f And the filter inductor is configured on the AC side of the two-stage grid-structured photovoltaic inverter.
As shown in fig. 4, in the embodiment of the present application, performing amplitude limiting processing on the voltage reference value through the positive sequence voltage loop and the negative sequence voltage loop, and obtaining the first positive sequence current reference value and the first negative sequence current reference value includes:
acquiring d-axis voltage positive sequence component u of grid-connected point of two-stage grid-forming photovoltaic inverter and power system dP Q-axis voltage positive sequence component u qP D-axis voltage negative sequence component u dN And a negative sequence component u of the q-axis voltage qN ；
In the positive sequence voltage loop, for a voltage reference value V acref And d-axis voltage positive sequence component u dP Carrying out comparison, PI integral control and amplitude limiting treatment to obtain a d-axis positive sequence current reference value i dPref (ii) a For positive sequence component u of q-axis voltage qP Comparison with 0, PI integral control, and amplitude limiting controlThen, a q-axis positive sequence current reference value i is obtained qPref ；
In the negative sequence voltage loop, the negative sequence component u is applied to the d-axis voltage dN Comparing with 0, PI integral control and amplitude limiting processing to obtain a d-axis negative sequence current reference value i dNref (ii) a For negative sequence component u of q-axis voltage qN Comparing with 0, PI integral control and amplitude limiting processing to obtain a q-axis negative sequence current reference value i qNref ；
Wherein the first positive sequence current reference value comprises a d-axis positive sequence current reference value i dPref And q-axis positive sequence current reference value i qPref (ii) a The first negative sequence current reference value comprises a d-axis negative sequence current reference value i dNref And q-axis negative-sequence current reference value i qNref 。
It should be noted that the parameter of the amplitude limiting process includes a d-axis output maximum amplitude limit value i of the positive sequence voltage loop dPLim Q-axis output maximum amplitude i of positive sequence voltage loop qPLim D-axis output maximum amplitude i of negative sequence voltage ring dNLim Q-axis output maximum amplitude i of negative sequence voltage loop pNLim 。
As shown in fig. 5, in the embodiment of the present application, the obtaining corresponding first positive-sequence valve-side reference voltage and first negative-sequence valve-side reference voltage by applying corresponding positive-sequence current loop, coordinate transformation, and negative-sequence current loop, and coordinate transformation processes to the first positive-sequence current reference value and the first negative-sequence current reference value includes:
obtaining d-axis actual measurement current positive sequence component i at outlet of two-stage type grid-forming photovoltaic inverter dP Q-axis actual measurement current positive sequence component i qP D-axis actual measurement current negative sequence component i dN And a negative sequence component i of the q-axis measured current qN ；
In the positive sequence current loop, for d-axis positive sequence current reference value i dPref Positive sequence component i of measured current with d axis dP Carrying out comparison, PI control and coordinate transformation to obtain a d-axis positive sequence valve side reference voltage component u cdP (ii) a For q-axis positive sequence current reference value i qPref Positive sequence component i of measured current with q axis qP Carrying out comparison, PI control and coordinate transformation to obtain a q-axis positive sequence valve side reference voltage component u cqP ；
In the positive sequence current loop, for d-axis negative sequence current reference value i dNref Negative sequence component i of measured current with d axis dN Carrying out comparison, PI control and coordinate transformation to obtain a d-axis negative sequence valve side reference voltage component u cdN (ii) a For q-axis negative sequence current reference value i qNref Negative sequence component i of measured current with q axis qN Carrying out comparison, PI control and coordinate transformation to obtain a q-axis negative sequence valve side reference voltage component u cqN ；
Wherein the first positive sequence valve side reference voltage comprises a d-axis positive sequence valve side reference voltage component u cdP And q-axis positive sequence valve-side reference voltage component u cqP (ii) a The first negative sequence valve-side reference voltage comprises a d-axis negative sequence valve-side reference voltage component u cdN And q-axis negative sequence valve side reference voltage component u cqN 。
S4, if the control signal is 1, obtaining second valve side reference data by adopting a second control mode according to the alternating voltage amplitude, the tolerant maximum current value and the rated current value, and controlling the operation of the rear-stage inverter circuit according to the second valve side reference data; and controlling the operation of the preceding stage booster circuit in a direct-current voltage mode.
If the control signal is 1, it is indicated that a symmetric or asymmetric ground fault occurs in the power system where the two-stage grid-connected photovoltaic inverter is located, the second valve-side reference data obtained by the second control method is needed to control the operation of the subsequent inverter circuit; and controlling the operation of the pre-stage booster circuit in a direct-current voltage mode. In the present embodiment, the dc voltage mode is a relatively well-known technical means in the art, and therefore, the content of the dc voltage mode will not be described in detail here.
Further, the obtaining of the second valve side reference data by the second control method according to the ac voltage amplitude, the maximum current tolerance value, and the rated current value includes:
acquiring a d-axis positive sequence current reference value before the fault of the two-stage type grid-forming photovoltaic inverter according to the control signal of 1;
calculating by adopting a network-building algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value; carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring; calculating and determining a second positive sequence current reference value and a second negative sequence current reference value according to the d-axis positive sequence current reference value, the alternating voltage amplitude, the tolerance maximum current value and the rated current value;
corresponding positive sequence current loops, coordinate transformation and negative sequence current loops and coordinate transformation processing are adopted for the second positive sequence current reference value and the second negative sequence current reference value, and corresponding second positive sequence valve side reference voltage and second negative sequence valve side reference voltage are obtained;
wherein the second valve side reference data comprises a second positive sequence valve side reference voltage and a second negative sequence valve side reference voltage.
In the embodiment of the application, from the fault of the power system where the two-stage grid-connected photovoltaic inverter is located to the control of the fault current by taking measures, a fault current peak can occur within a certain time delay. Therefore, the second control mode of the low voltage ride through control method of the two-stage grid-connected photovoltaic inverter can also adopt the first control mode to carry out amplitude limiting through the output of the positive sequence voltage ring and the negative sequence voltage ring according to the voltage reference value, and the current spike can be restrained before the fault current control measure takes effect (namely the second control mode takes effect), so that the current spike at the moment of the fault can be restrained. According to the low-voltage ride through control method of the two-stage grid-connected photovoltaic inverter, instantaneous current spikes can be effectively suppressed at the initial stage of a fault by setting the output amplitude limiting of the positive-sequence voltage ring and the negative-sequence voltage ring. So that the output current reference value needs to be limited within the maximum current value range which can be endured by the two-stage grid type photovoltaic inverter.
In this embodiment of the present application, the parameter of the clipping process may be represented by a first expression, where the first expression is:
in the formula i MAX The maximum current value which can be endured by the two-stage grid-connected photovoltaic inverter can be set according to the actual capacity of equipment. Wherein the parameters of the amplitude limiting process comprise a positive sequence voltage loopD-axis output maximum amplitude value i dPLim Q-axis output maximum amplitude i of positive sequence voltage loop qPLim D-axis output maximum amplitude limit i of negative sequence voltage ring dNLim Q-axis output maximum amplitude i of negative sequence voltage loop pNLim . In the present embodiment, i in expression one dPLim ＝i MAX D-axis current may be in the range of 0 to i MAX Internal variation, margin of remaining
The q-axis current is given a clipping.
In the embodiment of the application, the low voltage ride through control method of the two-stage grid-connected photovoltaic inverter adopts a current reference formula to calculate and determine a second positive sequence current reference value and a second negative sequence current reference value according to a d-axis positive sequence current reference value, an alternating voltage amplitude value, a tolerance maximum current value and a rated current value. The current reference formula is:
i dNref '＝0
i qNref '＝0
in the formula i d0 Is a d-axis positive sequence current reference value, U, before failure T Is the amplitude of the alternating voltage, I N Is a rated current value. When a three-phase short circuit or a two-phase short circuit occurs in an alternating current power grid of a power system where the two-stage grid-connected photovoltaic inverter is located, the U T Taking a line voltage; when the single-phase short circuit occurs in the alternating current power grid of the power system where the two-stage grid-structured photovoltaic inverter is located, the U T Taking the phase voltage, the voltage threshold for low voltage ride through may be set to 0.9p.u. And p.u. is a per unit value of the voltage of the power system where the two-stage grid-connected photovoltaic inverter is located. The second positive sequence current reference value comprises a d-axis positive sequence current reference value i dPref Positive sequence electric of' and q axesStream reference value i qPref '; the second negative sequence current reference value comprises a d-axis negative sequence current reference value i dNref ' and q-axis negative sequence current reference value i qNref '. d-axis positive sequence current reference value i dPref ' takes on a value from i d0 And
the minimum value in between.
It should be noted that, in the second control mode, the corresponding positive-sequence current loop, coordinate transformation, negative-sequence current loop, and coordinate transformation processing are applied to the second positive-sequence current reference value and the second negative-sequence current reference value, and the obtained corresponding second positive-sequence valve-side reference voltage and second negative-sequence valve-side reference voltage are the same as those in the first control mode, and the second valve-side reference data can be obtained by referring to the process of processing data in the positive-sequence current loop and the negative-sequence current loop in the first control mode. In this embodiment, the low-pass current reference value (including the second positive-sequence current reference value and the second negative-sequence current reference value) is sent to the positive-sequence current loop and the negative-sequence current loop to control the positive-sequence fault current and the negative-sequence fault current, respectively, and the pre-stage boost circuit is switched from the maximum power point tracking mode (MPPT control loop) to the dc voltage mode to realize the dc voltage control during the fault and the automatic balance of the photovoltaic output power. When the control mode is 1, a network construction algorithm, a positive sequence voltage ring and a negative sequence voltage ring of the rear-stage inverter circuit are locked, the output of the rear-stage inverter circuit is enabled to keep a value before a fault, and the maximum power point tracking mode of the front-stage booster circuit is locked, and the output of the front-stage booster circuit is enabled to keep the value before the fault.
The low voltage ride through control method of the two-stage grid-connected photovoltaic inverter comprises the steps of obtaining an electrical quantity parameter of the two-stage grid-connected photovoltaic inverter; determining a control signal for low-voltage ride through in the two-stage type grid-structured photovoltaic inverter according to the amplitude of the alternating voltage; if the control signal is 0, obtaining first valve side reference data by adopting a first control mode according to the actual reactive power value and the rated value of the alternating voltage, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; controlling the operation of the preceding-stage booster circuit by adopting a maximum power point tracking mode; if the control signal is 1, obtaining second valve side reference data by adopting a second control mode according to the alternating voltage amplitude, the tolerant maximum current value and the rated current value, and controlling the operation of the rear-stage inverter circuit according to the second valve side reference data; and controlling the operation of the pre-stage booster circuit in a direct-current voltage mode. According to the low voltage ride through control method of the two-stage grid-connected photovoltaic inverter, valve side reference data obtained by a first control mode and a second control mode with positive and negative sequence voltage and positive and negative sequence current control capacities are respectively adopted through control signals, and positive and negative sequence voltages are controlled to externally present voltage source characteristics; positive and negative sequence currents are controlled to flexibly control fault currents; the low voltage ride through of the two-stage type grid-forming photovoltaic inverter is realized through the matching of the control strategies of the preceding stage booster circuit and the subsequent stage inverter circuit, the balance of the photovoltaic output power during the fault period and the smooth transition from the fault period to the grid-forming control period are realized, and the technical problem that the operation of an electric power system is damaged by large current generated after the fault occurs when the photovoltaic inverter is applied to the grid-forming control technology in the conventional electric power system is solved.
In one embodiment of the present application, a low voltage ride through control method of the two-stage grid-connected photovoltaic inverter includes: if the fault is cleared, controlling the amplitude of the alternating voltage to be not smaller than a voltage threshold value, and restoring a second positive sequence current reference value and a second negative sequence current reference value in a second control mode to the position before the fault according to the slope ratio; and simultaneously, the direct-current voltage mode for controlling the operation of the pre-stage booster circuit is switched to the maximum power point tracking mode.
It should be noted that the slope ratio can be set according to the requirement, for example, the slope ratio is not lower than 30% of the rated current. If the fault is cleared, controlling the amplitude of the alternating voltage not to be smaller than a voltage threshold value, wherein the control signal is 0, and the reference values of the positive sequence current loop and the negative sequence current loop are restored to the value before the fault according to the slope proportion; and opening the output of a maximum power point tracking mode (also called MPPT control loop), switching the direct-current voltage mode of the front-stage booster circuit back to the maximum power point tracking mode control, and simultaneously reopening the network construction type algorithm and the positive and negative sequence voltage loop output of the rear-stage inverter circuit.
Example two:
fig. 6 is a block diagram of a low voltage ride through control device of a two-stage grid-connected photovoltaic inverter according to an embodiment of the present application.
As shown in fig. 6, an embodiment of the present application further provides a low voltage ride through control device for a two-stage grid-connected photovoltaic inverter, where the two-stage grid-connected photovoltaic inverter includes a preceding-stage boost circuit and a succeeding-stage inverter circuit, and the low voltage ride through control device includes a parameter obtaining module 10, a control judging module 20, a first execution module 30, and a second execution module 40;
the parameter obtaining module 10 is configured to obtain electrical quantity parameters of the two-stage grid-connected photovoltaic inverter, where the electrical quantity parameters include an actual reactive power value, an ac voltage rated value, an ac voltage amplitude value, a maximum tolerant current value, and a rated current value;
the control judgment module 20 is configured to determine a control signal for low-voltage ride through in the two-stage grid-connected photovoltaic inverter according to the ac voltage amplitude;
the first execution module 30 is configured to obtain first valve-side reference data according to the actual reactive power value and the rated ac voltage value in a first control manner according to that the control signal is 0, and control operation of the subsequent inverter circuit according to the first valve-side reference data; controlling the operation of the preceding-stage booster circuit by adopting a maximum power point tracking mode;
the second execution module 40 is configured to obtain second valve side reference data in a second control manner according to the ac voltage amplitude, the maximum tolerant current value, and the rated current value, and control the operation of the subsequent inverter circuit according to the second valve side reference data, where the control signal is 1; and controlling the operation of the pre-stage booster circuit in a direct-current voltage mode.
In the embodiment of the present application, the first execution module 30 includes a first computation sub-module, a first processing sub-module, and a second processing sub-module;
the first calculation submodule is used for calculating by adopting a network construction type algorithm according to the actual value of the reactive power and the rated value of the alternating voltage to obtain a voltage reference value;
the first processing submodule is used for carrying out amplitude limiting processing on the voltage reference value through the positive sequence voltage loop and the negative sequence voltage loop to obtain a first positive sequence current reference value and a first negative sequence current reference value;
the second processing submodule is used for carrying out corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing on the first positive sequence current reference value and the first negative sequence current reference value to obtain corresponding first positive sequence valve side reference voltage and first negative sequence valve side reference voltage;
wherein the first valve side reference data comprises a first positive sequence valve side reference voltage and a first negative sequence valve side reference voltage.
In the embodiment of the present application, the second execution module 40 includes a data obtaining sub-module, a second calculating sub-module, and a third processing sub-module;
the data acquisition submodule is used for acquiring a d-axis positive sequence current reference value of the two-stage type grid-forming photovoltaic inverter before the fault according to the control signal of 1;
the second calculation submodule is used for calculating by adopting a network construction type algorithm according to the actual value of the reactive power and the rated value of the alternating voltage to obtain a voltage reference value; carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring; calculating and determining a second positive sequence current reference value and a second negative sequence current reference value according to the d-axis positive sequence current reference value, the alternating voltage amplitude, the tolerance maximum current value and the rated current value;
the third processing submodule is used for performing corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing on the second positive sequence current reference value and the second negative sequence current reference value to obtain corresponding second positive sequence valve side reference voltage and second negative sequence valve side reference voltage;
wherein the second valve side reference data comprises a second positive sequence valve side reference voltage and a second negative sequence valve side reference voltage.
In the embodiment of the application, the low-voltage ride-through control device of the two-stage grid-connected photovoltaic inverter comprises a fault clearing module, wherein the fault clearing module is used for controlling the amplitude of the alternating voltage to be not less than a voltage threshold value according to fault clearing and restoring a second positive-sequence current reference value and a second negative-sequence current reference value in a second control mode to the positions before the fault according to a slope proportion; and simultaneously, the direct-current voltage mode for controlling the operation of the preceding-stage booster circuit is switched to the maximum power point tracking mode.
It should be noted that, the modules in the second embodiment device correspond to the steps in the first embodiment method, and the contents of the low voltage ride through control method for the two-stage grid-connected pv inverter are described in detail in the first embodiment, and the contents of the modules in the second embodiment device are not described in detail in this second embodiment.
Example three:
the embodiment of the application provides terminal equipment, which comprises a processor and a memory;
a memory for storing the program code and transmitting the program code to the processor;
and the processor is used for executing the low voltage ride through control method of the two-stage grid-connected photovoltaic inverter according to instructions in the program codes.
It should be noted that the processor is configured to execute the steps of the above-mentioned embodiment of the method for controlling low voltage ride through of a two-stage grid-connected pv inverter according to the instructions in the program code. Alternatively, the processor, when executing the computer program, implements the functions of each module/unit in each system/apparatus embodiment described above.
Illustratively, a computer program may be partitioned into one or more modules/units, stored in memory and executed by a processor to complete the application. One or more modules/units may be a series of computer program instruction segments capable of performing certain functions, the instruction segments being used to describe the execution of the computer program in the terminal device.
The terminal device may be a desktop computer, a notebook, a palm computer, a cloud server, or other computing devices. The terminal device may include, but is not limited to, a processor, a memory. Those skilled in the art will appreciate that the terminal device is not limited and may include more or fewer components than those shown, or some components may be combined, or different components, e.g., the terminal device may also include input output devices, network access devices, buses, etc.
The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like.
The storage may be an internal storage unit of the terminal device, such as a hard disk or a memory of the terminal device. The memory may also be an external storage device of the terminal device, such as a plug-in hard disk provided on the terminal device, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), and the like. Further, the memory may also include both an internal storage unit of the terminal device and an external storage device. The memory is used for storing computer programs and other programs and data required by the terminal device. The memory may also be used to temporarily store data that has been output or is to be output.
It is clear to those skilled in the art that, for convenience and brevity of description, the specific working processes of the above-described systems, apparatuses and units may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application, which are essential or part of the technical solutions contributing to the prior art, or all or part of the technical solutions, may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
The above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present application.
Claims (10)
1. A low voltage ride through control method of a two-stage grid-structured photovoltaic inverter is characterized by comprising a preceding stage booster circuit and a subsequent stage inverter circuit, and comprises the following steps:
acquiring electrical quantity parameters of a two-stage grid-forming photovoltaic inverter, wherein the electrical quantity parameters comprise a reactive power actual value, an alternating voltage rated value, an alternating voltage amplitude value, a maximum tolerant current value and a rated current value;
determining a control signal for low-voltage ride through in the two-stage grid-connected photovoltaic inverter according to the alternating-current voltage amplitude;
if the control signal is 0, obtaining first valve side reference data by adopting a first control mode according to the actual reactive power value and the rated value of the alternating voltage, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; controlling the operation of the preceding stage booster circuit by adopting a maximum power point tracking mode;
if the control signal is 1, obtaining second valve side reference data by adopting a second control mode according to the alternating voltage amplitude, the tolerant maximum current value and the rated current value, and controlling the operation of the rear-stage inverter circuit according to the second valve side reference data; and controlling the operation of the preceding stage booster circuit in a direct-current voltage mode.
2. The method for controlling low voltage ride through of a two-stage grid-connected pv inverter according to claim 1, wherein the obtaining the first valve-side reference data according to the actual reactive power value and the ac voltage rating by the first control method comprises:
calculating by adopting a network construction type algorithm according to the actual reactive power value and the rated alternating voltage value to obtain a voltage reference value;
carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring to obtain a first positive sequence current reference value and a first negative sequence current reference value;
performing corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing on the first positive sequence current reference value and the first negative sequence current reference value to obtain corresponding first positive sequence valve side reference voltage and first negative sequence valve side reference voltage;
wherein the first valve side reference data comprises a first positive sequence valve side reference voltage and a first negative sequence valve side reference voltage.
3. The method for controlling low voltage ride-through of a two-stage grid-connected pv inverter according to claim 1, wherein obtaining second valve-side reference data according to the ac voltage amplitude, the maximum tolerant current value, and the rated current value in a second control manner comprises:
acquiring a d-axis positive sequence current reference value before the fault of the two-stage type grid-forming photovoltaic inverter according to the control signal of 1;
calculating by adopting a network-building algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value; carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring; calculating and determining a second positive sequence current reference value and a second negative sequence current reference value according to the d-axis positive sequence current reference value, the alternating voltage amplitude, the tolerant maximum current value and the rated current value;
corresponding positive sequence current loops, coordinate transformation and negative sequence current loops and coordinate transformation processing are adopted for the second positive sequence current reference value and the second negative sequence current reference value, and corresponding second positive sequence valve side reference voltage and second negative sequence valve side reference voltage are obtained;
wherein the second valve side reference data comprises a second positive sequence valve side reference voltage and a second negative sequence valve side reference voltage.
4. The method of claim 1, wherein determining the control signal for low voltage ride through in the two-stage grid-connected photovoltaic inverter according to the ac voltage amplitude comprises: if the alternating voltage amplitude is smaller than the voltage threshold value, the control signal is 1, and the two-stage grid-connected photovoltaic inverter is indicated to be in fault in the power system; if the amplitude of the alternating voltage is not smaller than the voltage threshold value, the control signal is 0, and it is indicated that no fault occurs in the power system where the two-stage grid-connected photovoltaic inverter is located.
5. The method for controlling low voltage ride through of the two-stage grid-connected photovoltaic inverter according to claim 4, comprising: if the fault is cleared, controlling the amplitude of the alternating voltage to be not smaller than a voltage threshold value, and restoring a second positive sequence current reference value and a second negative sequence current reference value in the second control mode to the position before the fault according to a slope ratio; and simultaneously, switching a direct-current voltage mode for controlling the operation of the preceding-stage booster circuit into a maximum power point tracking mode.
6. The low-voltage ride-through control device of the two-stage type grid-forming photovoltaic inverter is characterized by comprising a preceding-stage booster circuit and a subsequent-stage inverter circuit, and the low-voltage ride-through control device comprises a parameter acquisition module, a control judgment module, a first execution module and a second execution module;
the parameter acquisition module is used for acquiring electrical quantity parameters of the two-stage grid-structured photovoltaic inverter, wherein the electrical quantity parameters comprise an actual reactive power value, an alternating voltage rated value, an alternating voltage amplitude value, a maximum tolerant current value and a rated current value;
the control judgment module is used for determining a control signal for low-voltage ride through in the two-stage grid-connected photovoltaic inverter according to the alternating-current voltage amplitude;
the first execution module is used for obtaining first valve side reference data by adopting a first control mode according to the actual reactive power value and the rated value of the alternating current voltage according to the control signal of 0, and controlling the operation of the rear-stage inverter circuit according to the first valve side reference data; controlling the operation of the preceding stage booster circuit by adopting a maximum power point tracking mode;
the second execution module is configured to obtain second valve side reference data in a second control manner according to the ac voltage amplitude, the maximum tolerant current value, and the rated current value, and control operation of the subsequent inverter circuit according to the second valve side reference data, where the control signal is 1; and controlling the operation of the preceding stage booster circuit in a direct-current voltage mode.
7. The low voltage ride through control device of the two-stage grid-connected photovoltaic inverter according to claim 6, wherein the first execution module comprises a first calculation submodule, a first processing submodule and a second processing submodule;
the first calculation submodule is used for calculating by adopting a network-building algorithm according to the actual reactive power value and the rated alternating voltage value to obtain a voltage reference value;
the first processing submodule is used for carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring to obtain a first positive sequence current reference value and a first negative sequence current reference value;
the second processing submodule is used for performing corresponding positive sequence current loop, coordinate transformation and negative sequence current loop and coordinate transformation processing on the first positive sequence current reference value and the first negative sequence current reference value to obtain corresponding first positive sequence valve side reference voltage and first negative sequence valve side reference voltage;
wherein the first valve side reference data comprises a first positive sequence valve side reference voltage and a first negative sequence valve side reference voltage.
8. The low voltage ride-through control device of the two-stage grid-connected photovoltaic inverter according to claim 6, wherein the second execution module comprises a data acquisition sub-module, a second calculation sub-module, and a third processing sub-module;
the data acquisition submodule is used for acquiring a d-axis positive sequence current reference value of the two-stage type grid-structured photovoltaic inverter before the fault according to the control signal of 1;
the second calculation submodule is used for calculating by adopting a network-building type algorithm according to the actual reactive power value and the rated value of the alternating voltage to obtain a voltage reference value; carrying out amplitude limiting processing on the voltage reference value through a positive sequence voltage ring and a negative sequence voltage ring; calculating and determining a second positive sequence current reference value and a second negative sequence current reference value according to the d-axis positive sequence current reference value, the alternating voltage amplitude, the tolerance maximum current value and the rated current value;
the third processing submodule is configured to perform corresponding positive-sequence current loop, coordinate transformation and negative-sequence current loop and coordinate transformation processing on the second positive-sequence current reference value and the second negative-sequence current reference value to obtain a corresponding second positive-sequence valve-side reference voltage and a corresponding second negative-sequence valve-side reference voltage;
wherein the second valve side reference data comprises a second positive sequence valve side reference voltage and a second negative sequence valve side reference voltage.
9. The apparatus for controlling low voltage ride-through of a two-stage grid-connected photovoltaic inverter as claimed in claim 6, comprising a fault clearing module for controlling the ac voltage amplitude to be not less than a voltage threshold value according to fault clearing and restoring a second positive-sequence current reference value and a second negative-sequence current reference value in the second control mode to a value before fault in a slope ratio; and simultaneously, switching the direct-current voltage mode for controlling the operation of the preceding-stage booster circuit into a maximum power point tracking mode.
10. A terminal device comprising a processor and a memory;
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the method for controlling low voltage ride through of the two-stage grid-connected photovoltaic inverter according to any one of claims 1 to 5 according to instructions in the program code.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN117269838A (en) * | 2023-11-22 | 2023-12-22 | 中国电力科学研究院有限公司 | Method and system for determining short-circuit current of network-structured power electronic equipment |
| CN117578621A (en) * | 2023-11-24 | 2024-02-20 | 国网江苏省电力有限公司泰州供电分公司 | Control method of grid-built inverter |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117269838A (en) * | 2023-11-22 | 2023-12-22 | 中国电力科学研究院有限公司 | Method and system for determining short-circuit current of network-structured power electronic equipment |
| CN117269838B (en) * | 2023-11-22 | 2024-01-30 | 中国电力科学研究院有限公司 | Method and system for determining short-circuit current of network-structured power electronic equipment |
| CN117578621A (en) * | 2023-11-24 | 2024-02-20 | 国网江苏省电力有限公司泰州供电分公司 | Control method of grid-built inverter |
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